There are different views out there about the best road to getting a novel or a screenplay noticed. Personally, I wouldn’t write a novel in order to get a movie made, or write a screenplay in the hopes of having it novelized.
Every art form needs to stand on its own. Novels don’t always translate well into movies since movies are more visual (external) and novels often include lots of internalization in the minds of the characters. Unless you rely on a voiceover, you would need to physicalize all internal struggles when translating a novel to film.
There is always a reductive quality to translating one art form to another. In other words, you’ll always lose something that the first art form offers when you translate it into another form. It’ll have to be changed, and in that change it must conform to the limitations of the second art form.
I tend to naturally write very cinematically. I flip point-of-view sections in my novels the same as a director might change camera angles or switch scenes to render the story from different characters’ points-of-view. Because of this, I think my novels will translate well into film. (And it is a possibility.)
A novel that’s printed by an established publisher has to go through many gatekeepers—an agent, an acquisitions editor, a publishing board, a project and copy editor, and proofreaders. Because of this, if you have a published novel, I think producers will take a more careful look at it than they might from an unknown screenplay writer.